In an electronic component mounting step, screen printing is used as a method of printing paste such as cream solder or conductive past on a board. In this method, a squeegeeing operation of supplying paste on a screen mask below which the board is set and sliding a squeegee is repeatedly performed. In this squeegeeing operation, the paste is raked up in the traveling direction of the squeegee and is gradually pushed outwards along the surface of the squeegee. The paste which is moved beyond the width dimension of the board remains in this range without being raked up by the squeegee due to the bending of the screen mask, attaches onto the top surface of the screen mask, and dries, hardens and deposits over time. In order to prevent low printing quality due to the deposits of the paste on the screen mask, a screen printing device is known which is constructed to provide a blocking and stopping member to prevent the paste from being overflown beyond the printing width in the squeegeeing (refer to a patent document 1).